Why is the middle dot of the face outside the face itself?
The ‘dot’ representing the face is positioned at the “centre” of all the vertices of that face - calculated as the average over all vertices. In your case you have a large ngon with many more than 4 vertices and the ‘average’ happens to be outside your mesh (drawn away due to all the vertices along the curve).

It isn’t a problem that the ‘centre’ of the face is outside the face itself but it might be a problem that the face is an ngon (more than 4 vertices) as it can cause problems further down the line (eg, when trying to animate or subdivide the mesh). It would be best to delete the face (X, Faces Only) and re-create it with better geometry (quads/tris).